Cursor shifter for slide rules



Feb. 9 1926. 1,572,497

H. A. M cARTER CURSOR SHIFTER FQR SLIDE RULES Filed June 1925 INVENTOR. K

L Har0ZdA.M 0arZer A TTORNE Y.

Patented Feb. 9, 1926.

HAROLD A. MCCARTER, OF LOS ANGELES, CALIFORNIA.

CURSOR SHIFTER FOR SLIDE RULES.

Application filed June 20, 1925.

To (:ZZ whom it may concern:

Be it known that I, HA OLD A. McCAnTnn, a citizen of the United States, residing at Los Angeles, in the county of Los Angeles and State of California, have invented new and useful Improvements in Cursor Shifters for Slide Rules, of which the following is a ieci licati on l lily invention relates to an attachment 101- use on slide rules.

The primary object of my invention is to prov de an attachment for use on the indicai'or or cursor of a slide rule by means of which it may be shifted without releasing the grasp of either hand on the slide rule, thus facilitating the manipulation thereof.

Another object is to provide a device of the character described which is simple in construction and which readily may be applied. to the cursor of any make of slide rules.

Other objects and advantages will appear hereinafter and while I show herewith and will describe a preferred form of construction, I desire it to be understood that I do not limit my invention to such preferred form but that various changes and adaptations may be made therein without departing from the spirit of my invention as hereinafter claimed.

Referring to the drawings which accompany this specification and form a part thereof:

Fig. 1 is a plan view of a slide rule, the cursor of which is equipped with my shifter attachment.

Fig. 2 is an enlarged fragmentary view of the rule shown in Fig. 1.

Fig. 3 is a sectional View of the rule, cursor and shifter taken on line 33 of Fig. 2.

l ig. 4 is a view in perspective of my cursor shifter detached from the rule.

Fig. 5 is a fragmentary view, similar to Fig. 2, of a different make of slide rule from that shown in the previous figures, showing my shifting device adapted for use with its cursor.

In Fig. 1 is shown a typical slide rule having grooved parallel bars rigidly held in spaced relation to each other by plates 1 secured to their ends and a double tongned slide-bar 12 slidably fitted between them. Scales (not shown) are marked on the sides of bars 10 adjacent their inner edges 13 and 1% and similar scales corresponding thereto are marked on the sides of slide bar 11 ad- Serial No. 38,575.

jacent its edges 15 and 16 respectively. An indicator or cursor 17, made of transparent plates 18 with spacing blocks 19 between their ends, extends across bars 10 and is slidably held at right angles thereto by a spring 20 attached to one of the spacing blocks. Longitudinal hair lines 21 are mar ted in the middle of cursor plates 18 by which the slide is properly adjusted and accurate readings are made.

hen making calculations with the slide rule the cursor frequently must be shifted and set; for new readings and in doing this it has been necessary to release the grasp of one hand on the rule occasionally so that it may be employed for that purpose; each operation of this kind involving an appreciable amount of time.

My attachment is designed to eliminate such necessity and consists of a piece of flatspr ing metal 22 bent to form an operating handle or lever 23 at one end and an attaching plate or clamp 21 at the other. The preferred form is shown in Figs. 2 and The clamp in this case is formed of resilient side flanges 25, made integral with the spring piece at right angles thereto, which flanges are adapted to engage the sides of one of said spacing blocks 19, which sides are cut away at their middle parts to form clearance spaces 19 throughout the greater part of their length. In their attached position as shown in Figs. 3 and 4t, flanges 25 are clamped between spacing block 19 and cursor plates 18 and are thus securely held in place.

The spring piece 22 is extended in longitudinal alignment with the clamp 24 to a point coinciding with one corner of the cursor as at 26, where it is bent at an angle somewhat less than 90 degrees and extended as at 27 toward the edge of the ruler. A second bend 28 is then made im a longer radius so that its convex face 29 makes contact with the outer edge 30 of one of the ruler bars 10. The second bend is made at such an angle that the second extension 31 makes an acute angle with the edge 30 of the ruler and this extension terminates in a loop 32 which serves as a thumb or finger hold, the latter extension and terminal loop constituting the lever 23 of the shifter.

The type of my slide rule shown in Fig. 5 has a modified form of cursor, consisting of a metal frame 33 adapted to engage edge grooves 04 in the parallel bars 35 and carrythereof is riveted to the side 39 of frame 33.

Other modifications may be made to adapt my shifter to different forms of cursors.

The cursor shifter being attached as shown in Fig. l and the right and left ends of the ruler being grasped by the right and left hands respectively of the operator in the usual way, the thumb of the left hand is applied to loop 32 of the lever and pressure is exerted thereon toward the edge 30 of the ruler, while the hand or thumb is moved to shift the cursor to the right or left as desired. The metal of the spring-piece 22 has sufiicient stiffness so that while yielding somewhat under pressure the handle acts as a lever arm, fulerumed on the convex face 29 which rests against the edge 30 of the ruler, the lever action operating to pull the end of the cursor, to which the shifter is attached, away from the ruler edge by the yielding of spring 20, so that during the process of shifting, contact with the ruler edges is made by the middle point of spring 20 and convex surface 29 of the spring-piece only.

\Vhen the ruler is reversed for readings on the opposite side from that shown, lever 23 comes on the upper instead of the lower edge of the ruler. In that position the forefinger instead of the thumb, is used for shifting the cursor. It is evident that, if preferred, the shifter may be attached to the cursor in a reversed position, so that it may be manipulated by a thumb or finger of the right instead of the left hand.

Having thus illustrated and described my invention I claim:

1. A cursor shifter comprising a spring lever, a thumb hold terminating said spring lever and means for attaching the opposite end of said spring lever to the cursor of a slide rule so that the spring lever engages one edge of the slide rule.

2. A cursor shifter comprising a spring lever terminating in a thumb hold at one end, a resilient clamp at the other end adapted for attachment to one end of a cursor on a slide rule, said spring lever having a compound bend between said thumb hold and said clamp whereby said spring lever is brought into engagement with one edge of a slide rule, with the lever arm extending at an angle therefrom.

3. In combination with a cursor on a slide rule, a cursor shifter comprising a spring lever having one of its ends attached to the cursor so that it extends along one edge of the slide rule, said spring lever having a compound bend adjacent one corner of said cursor whereby said lever is brought in contact with the edge of the slide rule with its free end extending at an angle therefrom, and a thumb hold terminating the free end of said spring lever whereby it may be manipulated to shift the cursor.

HAROLD A. iWIeCARTER. 

